The present invention relates to floor sweepers, and more particularly to a floor sweeper with an improved drive wheel construction.
It is already known, as shown in the above-identified patents, to construct a floor sweeper to drive a rotatable brush by means of free-floating drive wheels which are disposed in front and in back of a pair of coupling wheels that are located at opposite ends of the brush axle. This free-floating movement is such that when the sweeper is moved in one direction the drive wheels on one side of the brush contact the coupling wheels and rotate the brush by means of the downward pressure of the sweeper on the floor surface. At the same time, the drive wheels on the other side of the brush are moved out of engagement with the coupling wheels by this same pressure. When the sweeper is moved in the opposite direction, the operation of the drive wheels is reversed.
Although the above-identified Rosendall and Pullen patents show the drive wheels mounted on axles extending across the sweeper housing, it is also known from the above-identified Fukuba patent to mount the drive wheels on individual axles which can oscillate back and forth during movement across the floor. Additionally, it is known from the above-identified Pullen patent to provide wire springs which act against the drive wheel axles to urge these wheels toward the brush coupling wheels.
It is a task of the present invention to provide a floor sweeper with an improved drive wheel construction which is simple and economical to manufacture.
It is another task of the invention to provide a drive wheel construction that insures positive "loading" of the drive wheels with the bush coupling wheels when the sweeper is moved in one direction and "unloading" thereof when the sweeper is moved in the opposite direction.
It is a further task of the invention to provide a drive wheel construction which simultaneously "preloads" the drive wheels when moved into their unloaded positions. This preloading eliminates chattering of the drive wheel axles and insures that the drive wheels immediately move to their loaded positions to drive the brush coupling wheels when the direction of sweeper movement is reversed.
In accordance with one aspect of the invention, the sweeper incorporates spring means which pivotally mounts each of the drive wheels with respect to one of the brush coupling wheels for free movement between their loaded and unloaded positions. The spring means also provides an axle for rotatably mounting the drive wheel. The spring means includes a curved wire having a pair of bent legs extending transversely to the curve in the wire and parallel to the brush axle. The curved wire spring thus not only eliminates the need for a common axle for a pair of drive wheels but also loads the drive wheels by urging them into driving engagement with the brush coupling wheels when a downward pressure is applied against the sweeper by a user during movement of the sweeper in one direction over the floor. The pivotal connection of the curved wire spring enables the drive wheels to become unloaded from the coupling wheels when the direction of sweeper movement is reversed by reducing the amount of frictional force applied by the driving wheels against the coupling wheels. When this occurs, the opposite pair of driving wheels, which have now moved to their loaded positions, drive the coupling wheels to rotate the brush in the reverse direction.
In accordance with another aspect of the invention, the free end of the curved wire spring which forms the axle for the drive wheel rides along an inclined surface formed in an end partition of the sweeper sub-frame housing. The inclined surface forms a ramp that functions to preload the drive wheels in the direction of the coupling wheels when the drive wheels are in their unloaded positions by causing the wire spring to be compressed as the drive wheel moves away from the coupling wheel. This ramp insures that the drive wheels immediately move to their loaded positions to drive the coupling wheels upon reversal of the direction of movement of the sweeper. The ramp is inclined at an angle of about 7 degrees so that as the drive wheel moves further away from the coupling wheel a greater preloading force is applied thereto.